package com.jmex.effects.water;

/**
 * <code>ImprovedNoise</code>
 * Fast perlin noise.
 *
 * @author Ken Perlin
 */
public final class ImprovedNoise {
	public static double noise( double x, double y, double z ) {
		int X = (int) Math.floor( x ) & 255,				  // FIND UNIT CUBE THAT
				Y = (int) Math.floor( y ) & 255,				  // CONTAINS POINT.
				Z = (int) Math.floor( z ) & 255;
		x -= Math.floor( x );								// FIND RELATIVE X,Y,Z
		y -= Math.floor( y );								// OF POINT IN CUBE.
		z -= Math.floor( z );
		double u = fade( x ),								// COMPUTE FADE CURVES
				v = fade( y ),								// FOR EACH OF X,Y,Z.
				w = fade( z );
		int A = p[X] + Y, AA = p[A] + Z, AB = p[A + 1] + Z,	  // HASH COORDINATES OF
				B = p[X + 1] + Y, BA = p[B] + Z, BB = p[B + 1] + Z;	  // THE 8 CUBE CORNERS,

		return lerp( w, lerp( v, lerp( u, grad( p[AA], x, y, z ),  // AND ADD
									   grad( p[BA], x - 1, y, z ) ), // BLENDED
																	 lerp( u, grad( p[AB], x, y - 1, z ),  // RESULTS
																		   grad( p[BB], x - 1, y - 1, z ) ) ),// FROM  8
																											  lerp( v, lerp( u, grad( p[AA + 1], x, y, z - 1 ),  // CORNERS
																															 grad( p[BA + 1], x - 1, y, z - 1 ) ), // OF CUBE
																																								   lerp( u, grad( p[AB + 1], x, y - 1, z - 1 ),
																																										 grad( p[BB + 1], x - 1, y - 1, z - 1 ) ) ) );
	}

	private static double fade( double t ) {
		return t * t * t * (t * (t * 6 - 15) + 10);
	}

	private static double lerp( double t, double a, double b ) {
		return a + t * (b - a);
	}

	private static double grad( int hash, double x, double y, double z ) {
		int h = hash & 15;					  // CONVERT LO 4 BITS OF HASH CODE
		double u = h < 8 ? x : y,				 // INTO 12 GRADIENT DIRECTIONS.
				v = h < 4 ? y : h == 12 || h == 14 ? x : z;
		return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
	}

	private static final int p[] = new int[512], permutation[] = {151, 160, 137, 91, 90, 15,
														  131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
														  190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
														  88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
														  77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
														  102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
														  135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
														  5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
														  223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
														  129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
														  251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
														  49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
														  138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180
	};

	static {
		for( int i = 0; i < 256; i++ ) p[256 + i] = p[i] = permutation[i];
	}
}